In the sale and distribution of liquefied petroleum fuel gas (L.P. Gas) it is conventional for a distributor to use large above ground bulk storage tanks to store the highly volatile and inflammable liquid under substantial vapor gauge pressure and then distribute it to customers by delivery truck tanks that are filled repeatedly from the storage tanks through detachable liquid supply and vapor return conduits which include flexible stretchable hoses detachably connected to the truck delivery tank. These conduits are permanently connected to the bulk storage tanks and have automatic cut off flow control valves at the outlets to the hoses.
It is desirable that the conduits be quite flexible hoses to accommodate a random and quick positioning of a tank truck for rapid connection thereto and filling. Preferably the transfer hoses are short, approximately seven feet long, and are comparatively small in diameter for strength and ease of handling, and also for rapid filling while, for safety, minimizing the volume of liquefied gas present at any given time in the hoses between the tanks.
Aside from maintaining the handling and filling equipment in acceptably safe condition, an ever present random danger conventionally exists in which, occasionally, for any one of several reasons, a delivery truck driver receiving L.P. Gas will move his truck during filling, or drive his replenished truck away while the hoses are still connected between the truck tank and storage tank. This ruptures the hoses under substantial tension and there is pressurized spillage of liquefied gas that rapidly creates a highly dangerous fire hazard.
Automatic outflow cut-off transfer valves have been used where a trip cut-off cord is connected to the truck which upon drive away trips a valve. However, many times it has been found that the cord is not attached to the truck during filling operations nor can it be operated quickly by hand if desired.
In the present invention, the valves are automatically closed before a rupture occurs in either hose, or by presence of fire, and also provide a location where the filling attendant must stand to shut off flow immediately when danger occurs. By way of illustrating the invention, the check valve not only closes in the direction of outflow, but preferably equalizes pressures on opposite sides of a swing filler valve and closes it. It also closes the valve if a fire may already have been started from sparks, or any one of several other reasons, or the attendant sees danger, or the filling is completed, there being advantages in using safeguarding equipment regularly.
One of the objects of the invention is to compel the followance of a proper sequence in a truck tank filling procedure to manually and automatically prevent any hazardous spillage if there is inadvertant drive away without hose disconnection, or fire, and prevents any further use without attention and repair.
Another object of the invention is to control and limit any escape of hazardous material to only a readily dispersible known amount and confine any damage to equipment that is easily restored or replaced.
Another object is to assure good inspection, by regular use, testing and upkeep of safeguards provided for the ultimate prevention of dangerous break-away spillage and fires.
Other and further objects include the inhibition of liquid transfer except by personnel present if automatic equipment might be defective or improperly handled and provide readily available means for shutting down equipment under dangerous conditions.
More particularly, the safety cut off control can be used manually and serve as an instant manual shut off control when the delivery tank is filled to its proper level. Thereupon, with the shut off thus triggered and accomplished automatically, the setting of all controls and connections can be finalized for disconnecting the truck tank safely from the storage supply tank.